The main objective of this ongoing program is the systematic investigation of the anatomy and physiology of, and effects of pathological lesions on, the vestibulo-ocular system. The studies are conducted on cats and rabbits with normal or experimentally modified vestibulo-oculomotor systems. These studies are expected to provide quantitative information about vestibulo-ocular reflex responses, particularly those of nystagmus. This includes: 1) The elucidation of the contribution of individual receptors -- labyrinthine, visual and neck -- to the production of reflexes for gaze stabilization. 2) The development of models for the description of the production of both the slow and fast components of nystagmus. 3) Evaluation of the participation of the individual extrinsic nerve cells and muscles of the eye during each of the nystagmus components. 4) The comparison of the changes in vestibular responses due to abnormalities in the contributing elements of the vestibulo-ocular reflex arc with the prediction of models of vestibular function. A continued effort is being made toward the application of modern technology to the study of vestibular function. This includes the utilization of digital computers for the control of stimuli using deterministic and stochastic signals to the receptor organs, for the characterization of the parameters of the eye movements, and for parametric determination of the coefficients of transfer functions which describe the behavior of the vestibulo-oculomotor system.